Voice over IP portable transreceiver

ABSTRACT

Described below is a system to provide voice communication over a data network. The system is described as an access point connected to the data network adapted to exchange network messages over the data network and a wireless terminal including a transmitter component and a software module, the transmitter component adapted to exchange wireless messages with the access point over a wireless network, and the software module configured to provide a plurality of virtual channels. Each of the virtual channels being carried over the wireless network and the data network, the software module being configured to enable reception of the voice communication and to enable transmission of the voice communication over selected virtual channels.

PRIORITY CLAIM

The present application is a continuation application of U.S. patentapplication Ser. No. 10/338,938 filed Jan. 8, 2003 “Voice Over IPPortable Transreceiver”, the entire disclosure of which is expresslyincorporated herein by reference.

DESCRIPTION OF THE INVENTION

1. Field of the Invention

The present invention relates to methods and systems that provide voicecommunications over a data network.

2. Background of the Invention

In recent times there has been an increase in the use of portable twoway radios, commonly referred to as walkie-talkies, in a variety ofsettings. Walkie-talkies have been long used in work-related activities,for example to let employees remain in contact with one another and witha central office. Typical uses include warehouse and retail settings,where workers are requested to move goods, and where specific employeescan be summoned. Portable transreceivers are routinely used as analternative to telephone communications in any setting where thecommunicating users are relatively close to one another. The securityand public safety fields have been early users of walkie-talkies andrelated two way radio equipment, to help agents stay in contact andreceive instructions.

More recently, as two way radio devices have become less expensive,recreational and family uses have become increasingly common for thesedevices. Family members use simple walkie-talkies to stay in touch andfind each other, for example when hiking, skiing etc. Two way radios ofvarious levels of sophistication have found a place in all types ofsport and recreational events, to enhance safety and to increase theinformation level of the participants. Walkie-talkies have become almosta fashion accessory in certain cases, and have become available invarious shapes and colors, ranging from inexpensive low power units tosophisticated units capable of encrypting their transmissions.

Typical walkie-talkies and other types of two way radios, however,suffer from various drawbacks that limit their usefulness in manysituations. Perhaps the most serious limitation is the range of thesedevices, which often is very limited. Since the voice transmissions arecarried from one station to another by radio waves, any physicalobstacles to the propagation of those waves affects the range andquality of the received transmission. Most publicly availablenon-licensed 2 way radios are limited to a small power output (5 wattsor less), which further limits their range. Interference from otherradios or various sources of electromagnetic noise also affectsreception quality. In addition, there is no mechanism in conventionalradios to prevent two transmissions on the same frequency (or channel)from interfering with each other, without the source or the recipient ofeither transmission being aware of the interference. In many cases usershave to carry various electronic tools such as portable computers orscanners, and having to carry an additional transreceiver device can bevery cumbersome.

SUMMARY OF THE INVENTION

In one aspect, embodiments of the present invention include a system toprovide voice communication over a data network which has wireless voiceenabled terminals, access points connected to the data network adaptedto exchange network messages over the data network, and a transmittercomponent of each of the terminals adapted to exchange data with theaccess points over a wireless network. The system also includes asoftware module executing on each of the terminals configured to providea plurality of virtual channels, each of the virtual channels beingcarried over the wireless network. The software module is configured toenable reception of the voice communication from the terminals over aselected virtual channel, and to enable transmission of the voicecommunication to the terminals over the selected virtual channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows wireless voice enabled terminals connected to a datanetwork according to an exemplary embodiment of the present invention;

FIG. 2 shows a diagram representing a software architecture of a voiceenabled terminal according to an embodiment of the present invention;

FIG. 3 shows an exemplary voice enabled terminal according to anembodiment of the present invention; and

FIG. 4 shows an exemplary screen shot of the controls for the voiceenabled terminal according to one embodiment of the invention.

DETAILED DESCRIPTION

The present invention may be further understood with reference to thefollowing description and the appended drawings, wherein like elementsare referred to with the same reference numerals. Conventional portabletransreceiver radios, such as the Walkie Talkie™ manufactured byMotorola®, are used in a multitude of situations, both for pleasure andin work related settings. However, the performance of radio frequency(RF) based portable transreceivers is severely limited by inherentshortcomings of that technology. For example, the range of those radiosis limited by the power of the transmitter, and the terrain separatingtransmitter and receiver. Only receivers within the transmitter's rangecan be contacted. RF based portable transreceivers generally cantransmit on many channels, with each channel being assigned a discretefrequency so that only radios tuned to the same channel can receive thetransmission. However, multiple radios may be transmitting on the samechannel, so that a transmission from one radio may be “stepped over” byanother radio's transmission, and neither radio transmission can beheard.

The present invention uses a different technology to provide WalkieTalkie™-like functionality to a voice enabled terminal. In addition,several features that are not available with RF based portabletransreceivers may be implemented within the system according to thepresent invention. As will be described more fully below, communicationsbetween the voice enabled terminals travel over a data network, and thusare not subject to the same range limitations affecting RF baseddevices. There may be portions of the network that are based on radiocommunications, for example the sections connecting the wireless voiceenabled terminal to a network access point. However, these are generallyused over short distances, and do not affect the communications rangebetween the various voice enabled units. According to embodiments of theinvention, the voice enabled terminals have the “feel” and general usagecharacteristics of conventional RF portable transreceivers, so thattheir usage is intuitive to anyone familiar with the conventional RFunits.

FIG. 1 shows one exemplary embodiment of a voice over IP (VOIP) portabletransreceiver system, which mimics the functionality of RF based systemswhile incorporating additional features. In this embodiment, a pluralityof voice enabled terminals 10 are interconnected and can provide voicecommunications amongst each other. Typically, each terminal 10 is givento an user or group of users. Since terminals 10 are portable, they arecapable of connecting to a wireless network, and are sufficiently smallto be easily carried. For example, terminals 10 may be specificallydesigned to be used as portable transreceivers, or may be hand helddevices with different purposes, to which the portable transreceiverfunctionality has been added. In one embodiment, the terminal is basedon a personal digital assistant (PDA) such as those using the Windows®CE operating system, or similar. The PDA may be a multi purpose PDAexecuting a software module which provides the portable transreceiverfunctionality, or may be a more specialized unit such as a PDA-scannercombination, which is also usable to read bar codes. As will be apparentto those skilled in the art, different types of voice enabled terminalsmay be used to communicate over the same data network, as long as theyoperate under compatible protocols.

Voice enabled terminals 10 include a transmitter section including anantenna 12, which enables them to communicate without being connected towires. For example, a wireless local area network (WLAN) 14 may be usedto connect each of the terminals 10 to access points 20. As long as theterminal 10 is within radio transmission range of at least one accesspoint 20, the device can be used to communicate with any other terminals10. A multi purpose WLAN 14 can be used, or the WLAN 14 may be adedicated network used only for voice communications. Access points 20form the connection between WLAN 14 and the data network 16 to which allterminals 10 are ultimately connected. Access points 20 act as a two wayconduit, which receives radio transmissions from the transmitter sectionof terminals 10, and forwards the transmissions to the data network 16using the appropriate protocols. For example, an internet protocol suchas TCP/IP may be used to direct the transmission to its intendedrecipients on data network 16. Various levels of data processing may becarried out by access points 20, for example for error correction orencryption purposes.

Data network 16 is the principal means by which voice messages arecarried between terminals 10. This network can be any network useable totransmit data, such as between microprocessors, and may be a local areanetwork (LAN), a wide area network (WAN) or the Internet. Using a datanetwork to carry the voice communications gives a distinct advantage tothe system according to the invention. The range of the portabletransreceiver-like terminals 10 is restricted only by the extent of datanetwork 16. When the Internet is used for this purpose, the range ofterminals 10 can be essentially unlimited, as long as an access point 20connected to network 16 is within range of each of the users. Thestructure of data networks 16, such as the Internet, provides a certainamount of redundancy since in case of failure of certain segments of thenetwork other segments can be used to carry the data. In addition, aswill be described in greater detail below, the network protocolaccording to the present invention provides additional redundancy tominimize loss of data. The VoIP system of the invention thus is morerobust than conventional RF based portable transreceivers, which aresubject to disruptions and interference. The system according to theinvention may also provide security benefits compared to RF baseddevices. Since the transmissions travel over the airwaves only for shortdistances at low power, it is more difficult to intercept them. Also,since the signals are already in a form that can be used by amicroprocessor, encryption operations are easier to carry out, forexample using the Kerberos or Wired systems.

In one exemplary embodiment according to the present invention, the VoIPportable transreceiver (WT) system provides packet-based voicecommunication between users of wireless voice enabled terminals, such asthose based on PDA devices manufactured by Symbol Technologies. Theexemplary wireless terminals operate under the 802.11b standard forwireless LAN's, thus providing interoperability between products ofdifferent manufacturers. The exemplary embodiment uses direct sequenceradio frequency transmissions. However, frequency hopping spreadspectrum RF modes and other non RF modes, such as infraredtransmissions, may also be employed within WLAN 14. One benefit of usingthe 802.11b standard is that existing infrastructures using thatstandard may be adapted to support the VoIP WT system with minimalmodifications. Most voice enabled terminal devices supporting thatstandard may be used as the portable transreceiver handset, oftenrequiring simply a software upgrade to operate according to theinvention.

One of the most basic capabilities of the VoIP WT system according toembodiments of the present invention is that it provides the user withan interface consistent with conventional RF based systems. Theoperation of the VoIP WT system should appear familiar to usersaccustomed to conventional RF devices. In one exemplary embodiment,terminals 10 execute software modules that provide multiple “virtual”communications channels, which appear to the user as analogous to thedifferent frequency channels found on RF units. Each VoIP WT unit may beconfigured to have a primary channel that is used as the default channelfor transmitting and for receiving, but the user can set the terminal totransmit and receive on any other desired channel, and to monitor someor all the available virtual channels. In the exemplary embodiment, theVoIP WT is capable of receiving and transmitting over at least 256discrete channels. Although the exemplary unit is capable of receivingany or all of those 256 channels, those of skill in the art willunderstand that all the channels must still travel over a common WLAN,since there is no separate network for each channel. Accordingly,irrespective of the number of channels supported by the VoIP WT, thesystem can deliver simultaneously only as many messages as can besupported by data networks 14 and 16. The number of simultaneousmessages that can be processed depends on the 802.11b networkarchitecture and on the specific site implementation.

In one embodiment, a channel may be dedicated as a priority channel, forexample to be used for high priority security messages. All the unitsconnected to the data network, such as terminals 10 on network 16, willreceive the priority channel, and the messages received on the prioritychannel will override any other messages transmitted on differentchannels. When a message on the priority channel is received, all theunits that are transmitting a message will abort the transmission, andnotify the user that the transmission was discontinued. For example, anaudible alert may be provided to the user for that purpose. Units thatare in the receive mode will be prevented from starting a transmissionwhile a priority message is being broadcast. All the units may have theability to broadcast on the priority channel, or that feature may onlybe reserved for selected units.

When the portable transreceiver according to the present invention isnot active on the default channel or on the priority channel, it iscapable of monitoring any of an assigned group of channels for incomingtransmissions. However, before the unit is able to transmit on one ofthe monitored channels, a specific channel must be selected by the user.In another embodiment, units may be given the ability to transmit onmultiple channels. Selecting a channel for transmission does not affectthe channel that has been defined as the default channel fortransmission and reception in a unit, which is also referred to as thedesignated primary channel of the unit. If a unit receives more than onemessage on different channels, which message is actually processed bythe unit depends on a specific priority scheme. Priority or securitybroadcasts are handled first, so they are always played to the user.Priority messages are followed by messages broadcast on the unit'sdesignated primary channel, and finally by broadcasts on any other ofthe monitored channels. Messages that are received on the monitoredchannels are not interrupted by another, later message with the samepriority level. Within messages of the same priority, the earlierreceived message is played.

Conventional RF based portable transreceiver units do not have anymechanism to prevent more than one unit from simultaneously broadcastingon the same channel when the users press the PTT switch. The VoIP WTsystem according to the invention provides a mechanism to prevent thiscollision of transmissions. Before a transmission is permitted by one ofthe units, software in the unit is configured to verify that the channelselected is not already in use. If the selected channel is not in use,the transmission is broadcast normally. If, when the user presses thePTT switch a message is already being received on that channel, thetransmit mode of the unit is disabled and a notification is issued tothe user to indicate that the selected channel is busy.

Despite these precautions, a race condition can take place when two ormore units have their PTT switches pressed simultaneously, while usingthe same channel. In that case, multiple portable transreceiver unitsmay be allowed to begin their transmission streams. The race can beresolved by configuring each voice enabled terminal unit in the systemso that no more than one message is heard by all the units on thechannel, to prevent any two listeners from hearing different messagesafter the collision has been detected. Once a VoIP WT unit that istransmitting detects another transmission on the same channel, one ofseveral acceptable actions may be taken. For example, all the units maystop transmitting, and may provide to the relevant users a notificationof the race condition. Alternatively, a priority mechanism may bespecified, to allow only one of the transmissions to continue, whilesuppressing all other interfering transmissions. As will be apparent tothose skilled in the art, different priority schemes may be envisionedto prevent a broadcast collision from occurring. The principalrequirements for this are that only one transmission per channel at atime be received by the users, and that the relevant users be notifiedwhen their transmission is suppressed.

As shown in FIG. 1, a directory server 22 may be connected to the datanetwork 16 to provide a naming service for the system. A “group”, in thecontext of the present invention, is a named list of users thatsubscribe to a particular channel. The VoIP WT system supports a commondirectory based on server 22 which allows the management of user groups.The implementation of this functionality requires the presence of acentralized server 22, and will thus be optional. The directory serviceis used to correlate a group name to a channel number, so that usersdon't have to remember which channel numbers correspond to which set ofusers. For example, a user may request that the VoIP WT unit monitor the“Purchasing” or the “Loading Bay 1” groups, without having to rememberwhich channel numbers are associated with those groups. Changes tochannel membership are centralized under this system, which simplifiesmaintenance of the groups information. In one example, a public API maybe used to provide an application directory access to a centralizeddirectory hosted on a server using the lightweight directory accessprotocol (LDAP). Alternatively, the application directory may access alocal directory implemented in a static text file. One suitable LDAPdirectory server may be a server running Windows 2000®, particularlyusing Active Directory® software.

The system according to embodiments of the present invention can alsoprovide a telephone-like caller ID on each terminal, which indicates toeach user an identification of who originated a transmission. Thisfeature of the terminals is not dependent on the directory servicedescribed above, although in some cases the directory service may betied to the identification function. To provide the caller ID feature, aname that identifies either the unit or the person using the unit issent in the transmission, together with the data packets describing thevoice communication and any other pertinent data. Each receiving unitcan then display the name of the sender or the originating terminal, asapplicable.

Another feature that can be provided in a VoIP WT unit is theintegration of a peer-to-peer private mode with the traditional portabletransreceiver mode of operation. Traditional RF based WT units can onlyprovide a one-to-many broadcast mode, where the transmission is halfduplex, meaning that only one user at a time may speak. This isreplicated in the WT mode of operation of the VoIP WT system. Theprivate mode permits one-to-one calling between two users, with fullduplex transmissions in which both addressees may speak simultaneously.This mode provides the same functionality as a telephone call betweenthe two users. In one exemplary embodiment, a user at a receiving unitwill be able to initiate a private callback to the initiator of thelast, or most recently active WT mode message. In addition to theincreased privacy aspects of using the private mode, additional benefitsinclude reduced broadcast traffic, minimized distractions to other usersnot party to the peer-to-peer communication, and extended operating lifeof the non-participating units due to lower battery usage. This ispossible since only two units participate in a private modecommunication. Instead of tying up every terminal unit tuned to aspecific virtual channel in the WT mode, users can select the privatemode to limit communications to the two participating units.

Specialized message traffic rules may be used to prioritize thereception of peer-to-peer mode messages and of the normal WT modemessages. For example, if a WT mode message is received while the unitis participating in a peer-to-peer call, the peer-to-peer call is givenhigher priority. The user may be given a notification that a message isbeing received under the WT mode, and may be given the option ofswitching back to the WT mode of operation. In general, when a WT modemessage has been received by a unit, the user can be given the option ofresponding to the message by using the normal broadcasting WT mode, orby using the private peer-to-peer mode. Selection of the WT mode may bemade by simply pressing the PTT button of the unit. Peer-to-peer modemay be initiated by a separate soft or hard key, since it is not thedefault mode of operation of the VoIP WT device.

Another feature that is unique to the VoIP WT system according toembodiments of the present invention is the ability to store messagesfor future replay. In one embodiment, each portable transreceiver unitincludes a memory that can buffer the most recent incoming voice messageto provide a replay capability. In one embodiment, if the message islonger than the configured buffer size, only the last portion of themessage will be saved. The user will then be able to replay the bufferedmessage. In the case that a message is received while an earlier messageis being played back, playback of the buffer may be interrupted topermit reception of the new message, particularly if the new message isreceived on the priority channel. An audio alert may be used to furthernotify the user that buffer playback has been suspended to receive areal-time message. In one exemplary embodiment, the buffer may besufficient to store about 60 seconds of message.

According to embodiments of the invention, the VoIP WT system isdesigned to minimize network loading as much as practical, since it mustoperate in a network that is used also by other types of networktraffic. Latency of the WT system is reduced as much as possible, but toa certain extent is dependent on the actual network architecture.Latency of the half-duplex WT mode is not as critical as latency of thefull-duplex private mode, since in WT mode multiple participants cannotspeak simultaneously but instead have to take turns speaking. Thenetwork protocol chosen for the invention takes advantage of thislessened requirement of the WT mode to include redundant transmission ofthe voice data. This adds some latency to the message, but greatlyimproves the quality of the message. The redundant transmission allowsthe receiver to reconstruct missing voice data due to networkinterference or errors.

In one embodiment, the latency in the WT mode from the microphone of thetransmitting unit to the speaker of the receiving unit averages lessthan 500 milliseconds, excluding network delays. In the peer-to-peer orprivate mode, the latency from the transmitter's microphone to thereceiver's speaker is less than 300 milliseconds, also excluding networkdelays. Various signal compression methods may be used to reduce theamount of bandwidth used by the VoIP WT application. For example, aG.729A codec is provided for voice compression, however other moreeffective methods may also be incorporated.

FIG. 2 is a diagram showing an exemplary embodiment of the softwarearchitecture and hardware interface used to control a VoIP WT unit suchas the voice enabled terminal 10. FIG. 2 shows the software as appliedto a PDT8100X3 platform, manufactured by Symbol Technologies®, using the802.11b protocol. The exemplary platform is a hand help PDA that alsoincludes a bar code scanner in addition to the portable transreceiverfeatures, and is particularly useful where users need to communicatewith one another and to identify merchandise, such as in a warehouse. Itwill be apparent to those of skill in the art that a similar softwarearchitecture can be used in different voice enabled devices, withoutaffecting the functionality of the device. In the example, an hardwareinterface 50 includes the PDT8100X3 unit 52 and a Spectrum 24 adapter 54having a radio network card with a transmitter/receiver used to connectterminal 10 to the access points 20 via WLAN 14. The hardware componentalso includes a digital signal processor (DSP) 56, used to process thevoice communications, such as to perform signal compression tasks.

The software components include software elements 60 that are part ofthe Windows CE® operating system, and software elements 70 that arespecific to the portable transreceiver application, both of which areexecuted on a processor of the voice enabled device. It will be apparentthat other operating systems adapted to run on portable devices may beused, such as Palm® operating systems, etc. Windows CE® operating systemcomponents 60 are well known in the art, and include Wave in and outmodules 62 to process sounds, Winsock module 64 to manage networksockets, and various drivers 66 for the display screen, etc. Additionalsoftware modules may be included with software elements 70, which aredeveloped specifically to manage operation of the VoIP WT functionality.The WT application module 72 is the primary application that enablesterminal 10 to be used as a portable transreceiver. WT applicationmodule 72 is designed to minimize interference with other applicationsthat may be executed simultaneously on the unit, in particular otherapplications that use the notification driver 86 to provide audio cues.

Generally, the WT application module 72 operates in the background onthe device, so that the full screen of the device (i.e. terminal 10) maybe used for other applications. The application interface may bedisplayed automatically when needed, such as when an incoming message isdetected. If the user needs to see the VoIP WT application interface,for example to see the caller ID function, a “display pop” key may beprovided to toggle the WT application interface from the background tothe foreground, and vice versa, each time it is pressed. This toggle keymay be a physical button or a touch screen region of the device. Tomaximize battery life, the user has the option of operating in a lowpower mode, which may be entered by using a key. This mode blanks thescreen and may perform other functions to reduce power consumption. Inpower save mode the unit is fully functional and can send or receivevoice messages. If the user wants to see the screen, a key may bepressed to resume normal operations. If an event occurs which requiresthe user to see the screen, normal mode may be resumed automatically.

Private call transport module 74 enables the terminal 10 to be used inprivate mode communications, as described above. This mode uses, forexample, the H.323 session protocol for telephone-like full duplexperformance. Private call transport module 74 typically does not providesession control, since that is handled by the H.323 protocol. In oneembodiment, the application accesses H.232 for session control throughthe Microsoft Telephony API (TAPI). The Telephony service provider (TSP)manages call setup, call tear down and call control via the H.323 stack,and negotiates a common compression codec with the destination unit. Toprolonge battery life, module 74 may also include power managementfunctions, such as switching the unit between the power save mode (PSP)and the full power mode (CAM) as necessary.

To maximize battery life the unit normally operates in the lowest powermode. When a transmission is made, the unit is switched to full-powermode. When the unit is in standby mode, for example when waiting for anincoming message, the unit watches for a wake-up message, which is sentprior to a transmission as part of the protocol. If a wake-up message isreceived, the unit switches to full power mode. Since it is possible fora wake-up message to be lost, the radio also watches for regular voicepackets. Therefore, if one of the regular voice packets is detected, theunit is also turned on to full power mode. After the last packet in atransmission is received, the unit waits a short time interval to see ifadditional packets will be received. If there are no additional datapackets within a specified timeout period, the unit switches back intothe low-power mode.

The normal portable transreceiver mode of operation for terminal 10 isimplemented through WT call transport module 76. Module 76 providesone-to-many half duplex communications that replicate the functioning ofa RF portable transreceiver. In the exemplary embodiment the voicesignals are sent using a multicast realtime transport protocol (RTP)standard for streaming, using a packet switched network. WT calltransport module 76 also provides a method to increase the audio qualityof the transmission over an unreliable network. Since transmission overa data network can be unreliable and subject to various data errors,some form of error correction mechanism is required. The transmission ofvoice data must occur in real time, thus re-broadcasting the datapackets representing the voice communication is not feasible. Accordingto embodiments of the invention, a simple redundancy scheme is used, inwhich each voice data packet is transmitted multiple times, and isreassembled at the receiver. Any missing information from any of thetransmissions is likely to be present in the redundant transmission. Inone exemplary embodiment, two redundant packets are used, resulting ineach voice sample being sent three times.

The directory service described above is implemented through thedirectory services module 78 of software elements 70. Directory servicesmodule 70 manages the interaction with server 22, which provides namingservices for groups of users. Additional modules that are part of thesoftware elements 70 include the firmware and the drivers 84 that managethe operation of the spectrum 24 adapter, to enable the radiocommunications to access WLAN 14. Also included is a voice compressionservices module 80, which carries out voice compression operations toreduce the amount of network traffic required to transmit the voicedata. In the exemplary embodiment, module 80 interacts with the firmwareand driver 82 providing G.729A codecs for compression, which is carriedout by the digital signal processor 56. It will be apparent to thoseskilled in the art that the software architecture describe herein isexemplary only, and that the same functionality may be obtained usingdifferent operating systems and software configurations.

FIG. 3 shows a perspective view of an exemplary voice enabled terminal100 according to the invention. Terminal 100 is based on SymbolTechnologies' PDT8100X3 portable data terminal, and includes atransmitter/receiver component 102 used to connect with WLAN 14. Forexample, transmitter/receiver component 102 may be a Spectrum 24wireless network radio card used to transmit outbound voicecommunications and receive inbound voice communications. The primarycomponents of terminal 100 are a microphone 104 and a speaker 106 whichare adapted to reproduce the frequency range of human voice. Remotespeakers and microphones may also be provided, connectable to terminal100 with jacks. A push to talk (PTT) button 108 is included to initiatea transmission, as is done in RF portable transreceivers and CB radios.Although this function could be carried out with a soft key or a screencommand, a physical PTT button is more natural and easy to use. In caseswhere the unit is usable for multiple purposes, PTT switch 108 may alsoperform different functions, depending on which application is beingexecuted by terminal 100. A display 110 may also be included to presentto the user a graphical interface to access the VoIP WT system and otherapplications. A keyboard 112 may be provided, to enter commands and toselect options within the WT application, and for other applicationsthat are executable by terminal 100.

An exemplary screen shot of display 110 is shown in FIG. 4. In thisexample, the WT application runs under the Microsoft Windows CEoperating system, or the Microsoft Pocket PC 2002 operating system. Asindicated above, the PTT switch is preferably a physical switch, butother functions of the WT application may be selected using soft keysand/or the touchscreen 110 of the device. Normally the WT applicationexecutes as a background process, and only shows as a small icon on thePDA's display. When a transmission is received, the WT application isactivated, and a display such as display 120 is shown. Display 120 ispreferably designed to follow the operating system's convention, such ashaving a top bar 122 with the name of the application and a button tominimize the window. A status area 124 may be provided to indicatewhether the portable transreceiver system is idle, operating in the WTmode, or in the peer-to-peer mode. Additional status messages may bedisplayed as necessary. A pair of touch sensitive keys 126 can be usedto select the channel to be monitored and the channel to be used fortransmitting. The channel number is displayed in field 130, and thechannel name in field 128. If required, submenus may be provided toselect multiple channels or groups to be monitored. A directory key 132is used to bring up additional screens that allow the user to access thenaming service of server 22.

Several other functions of the WT application may be selected eitherwith physical buttons or touch sensitive areas of the display. Forexample, a volume bar 134 and muting button 136 may replace orsupplement physical volume controls of terminal 100. A replay button ortouch sensitive area 138 can be used to play back a portion of thelatest received voice message, and an additional screen may be invokedto let the user set recording and playback parameters. A callback area140 is provided to let the user initiate a peer-to-peer communicationwith another user. In a simple form, when key 140 is pressed, the userthat originated the last communication received would be called back. Inmore sophisticated applications, a different screen may be providedwhich lets the user select whom to contact in the peer-to-peer mode.Additional screens may be provided as needed, to let the user selectoptions and set parameters for the various functions of the WTapplication. A “tools” key 142 may be provided to access functions notshown on primary screen 120. It will be apparent that the specificscreen configuration and layout of the physical controls and touchscreen areas can vary depending on the design of the unit and theoperating system being used.

The present invention has been described with reference to specificembodiments associated with a multi purpose PDA running the Windows CEoperating system. However, other embodiments may be devised that usedifferent platforms and software without departing from the scope of theinvention. Accordingly, various modifications and changes may be made tothe embodiments without departing from the broadest spirit and scope ofthe present invention as set forth in the claims that follow. Thespecification and drawings are accordingly to be regarded in anillustrative rather than restrictive sense.

1. A system to provide voice communication over a data network,comprising: an access point connected to the data network adapted toexchange network messages over the data network; and a wireless terminalincluding a transmitter component and a software module, the transmittercomponent adapted to exchange wireless messages with the access pointover a wireless network, the software module configured to provide aplurality of virtual channels, each of the virtual channels beingcarried over the wireless network and the data network, the softwaremodule being configured to enable reception of the voice communicationand to enable transmission of the voice communication over selectedvirtual channels.
 2. The system according to claim 1, wherein theterminal are a voice-enabled terminal.
 3. The system according to claim1, wherein the software module is configured for at least one of (i)enabling half duplex transmission and reception on the virtual channels,(ii) preventing collision of transmissions on each of the virtualchannels, (iii) prioritizing simultaneous transmissions on each of theselected channels, such that only one of the simultaneous transmissionsis enabled, (iv) initiating a peer to peer full-duplex call with afurther wireless terminal, (v) transmitting redundant data packetsrepresenting the voice communication.
 4. The system according to claim1, wherein the terminal includes at least one of a speaker and a PTTswitch.
 5. The system according to claim 3, wherein transmission on anactive channel is disabled when the active channel is in use.
 6. Thesystem according to claim 3, wherein a user notification is generatedwhen initiating transmission on one of the selected channels if theselected channel is in use.
 7. The system according to claim 1, furtherproviding a priority channel enabled to override transmission andreception on the plurality of virtual channels.
 8. The system accordingto claim 3, wherein the wireless terminal receives a voice transmissionfrom the further wireless terminal over one of the plurality of virtualchannels.
 9. The system according to claim 3, wherein the peer to peerfull duplex call overrides reception and transmission of the voicecommunication over the plurality of virtual channels.
 10. The systemaccording to claim 1, wherein the wireless terminal includes a memoryadapted to store and replay a portion of the voice communication. 11.The system according to claim 1, further comprising a directory serviceof the data network adapted to associate names with the virtualchannels.
 12. The system according to claim 1, wherein the softwaremodule compresses data packets representing the voice communicationbefore transmission.
 13. A portable terminal comprising: a memorystoring software instructions; a transmitter section adapted forexchanging data with an access point via a wireless network, the accesspoint being connected to a data network; and a processor adapted toexecute the software instructions, the software instructions comprising:instructions to provide a plurality of virtual channels carried over thewireless network and the data network; instructions to generate datapackets representing an outbound voice communication, and transmit thedata packets over selected ones of the virtual channels; andinstructions to receive data packets over the selected ones of thevirtual channels and regenerate an inbound voice communication from thedata packets.
 14. The terminal according to claim 13, wherein theprocessor further comprises instructions for at least one of (i)establishing semi duplex communications over selected ones of thevirtual channels, (ii) establishing a full duplex communication with aselected addressee, (iii) disabling transmission of the data packetsover a virtual channel that is in use, (iv) transmitting the datapackets redundantly and (v) monitoring selected ones of the virtualchannels for the data packets.
 15. The terminal according to claim 13,further comprising a digital signal processor adapted for compressingthe data packets.
 16. The terminal according to claim 13, furthercomprising a push to talk button.
 17. The terminal according to claim13, further comprising a memory module adapted for storing the inboundvoice communication.
 18. The terminal according to claim 13, furthercomprising a display adapted to show a user interface of the softwareinstructions.
 19. The terminal according to claim 18, wherein thedisplay shows an origin identification of the inbound voicetransmission.
 20. The system according to claim 13, Wherein the terminalis a voice-enabled terminal.
 21. A method for conducting voicecommunications over a data network, comprising: providing a plurality ofvirtual channels carried over a wireless network and the data network;transmitting data packets representing an outbound voice communicationover a selected one of the virtual channels by a first wirelessterminal; receiving the data packets over the selected one of thevirtual channels by a second wireless terminal; and regenerating aninbound voice communication from the data packets by the second wirelessterminal.
 22. The method according to claim 20, further comprising:establishing one of full duplex and semi duplex communications over theselected one of the virtual channels
 23. The method according to claim20, further comprising: disabling transmission of the data packets overa virtual channel that is in use.
 24. The method according to claim 20,further comprising: transmitting the data packets redundantly.
 25. Anarrangement for conducting wireless communications, comprising: astorage means for storing software instructions; a communication meansfor exchanging data with an access point via a wireless network, theaccess point being connected to a data network; and a processing meansadapted to execute the software instructions, the software instructionscomprising: instructions to provide a plurality of virtual channelscarried over the wireless network and the data network; instructions togenerate data packets representing an outbound voice communication, andtransmit the data packets over selected ones of the virtual channels;and instructions to receive data packets over the selected ones of thevirtual channels and regenerate an inbound voice communication from thedata packets.